The Great Blue Hole, which is the largest ocean sinkhole in the world, created by a collapsed underground cavern, hence giving the appearance of a dark blue circle amidst the turquoise sea. The Blue Hole measures 1,000 ft in diameter and 460 feet in depth.

It is located approximately 60 miles East from Belize City and in March of 1996 it was declared a World Heritage Site and later declared a National Monument in February of 1999.